Generates a randomised string of characters 999 MegaBytes large once and repeats it while writing it into a file the amount of times it's necessary to get your desired size. Should give you an exact amount and not a rough estimate, but don't quote me on that
Does what I need it to do in as efficient way as I need it to (maybe a bit more efficient than necessary, but I got carried away), I will fix bugs if any are found but this will most likely not get any new features in the future.
Feel free to fork it and make it your own if you need something similar